AT SOME POINT IN THE HISTORY of civilization, shepherding gave way to farming. That created a need for some way of keeping cows and pigs from wandering freely through the meadows. The fence was born. Wooden fences were among the earliest, but they are expensive and time-consuming to build. By 1870 smooth cable was easy to get hold of and came into wide use on ranches. Cattle would rub their back on the wire, and sometimes one would slip through. Eventually the herds caught on.

That got Michael Kelly, an inventor from New York City, wondering how he might make the wire less comfortable as a bovine back scratcher. He got the idea to twist bits of sharp pointed wire onto ordinary cable, and in 1868 he patented his “thorny fence.” It was a big success—and a magnet for lawsuits. “Almost overnight it developed into a source of wealth and furious litigation colored by impassioned charges and countercharges of patent infringement and greed,” says historian Robert T. Clifton.